Guardiola enjoyed great success during a four-year reign at Camp Nou, with his haul of honours including three La Liga titles and two UEFA Champions League crowns.
However, Guardiola called time on his stay with the Catalan club at the end of the 2011-2012 season and subsequently took a year's sabbatical before joining Bundesliga champions Bayern Munich ahead of the present campaign.
The Spaniard pointed to Barca's semi-final defeat to Chelsea in the 2012 Champions League as a key point, when he knew it was right to depart, and says the club's immense success also played a part in his exit.
"There were many moments of sadness and that (losing to Chelsea) was one of them," Guardiola said in an interview with Autopista magazine.
"We were much better than our opponents but we conceded an unnecessary goal and before we knew it, we were out.
"It was a great loss to me. I thought I couldn't go back and set up the team again. If you can no longer motivate the players, as a coach, you know that the time has come to leave.
"We were incredibly successful - 14 trophies in four years. But that can also weigh you down.
"I was having difficulty motivating myself as well as the team, having won everything as a player and a coach. And the team was finding it increasingly difficult.
"The sabbatical year in New York was important to me, my family and to my old team."
Guardiola is now charged with the task of building on Bayern's unprecedented success under Jupp Heynckes, after the Bavarians collected a treble of the Bundesliga, DFB-Pokal and Champions League last season.
Bayern are currently on course to match that effort, with the club unbeaten in Germany's top flight and into the quarter-finals of the Champions League and semi-finals of the DFB-Pokal.
Guardiola added: "The challenge for me now is to work with a new team and continue the success of Jupp Heynckes. I have the opportunity to build a diverse team."
